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      1 /*
      2 **************************************************************************
      3 * Copyright (C) 1999-2005, International Business Machines Corporation and
      4 * others. All Rights Reserved.
      5 **************************************************************************
      6 *   Date        Name        Description
      7 *   11/17/99    aliu        Creation.  Ported from java.  Modified to
      8 *                           match current UnicodeString API.  Forced
      9 *                           to use name "handleReplaceBetween" because
     10 *                           of existing methods in UnicodeString.
     11 **************************************************************************
     12 */
     13 
     14 #ifndef REP_H
     15 #define REP_H
     16 
     17 #include "unicode/uobject.h"
     18 
     19 /**
     20  * \file
     21  * \brief C++ API: Replaceable String
     22  */
     23 
     24 U_NAMESPACE_BEGIN
     25 
     26 class UnicodeString;
     27 
     28 /**
     29  * <code>Replaceable</code> is an abstract base class representing a
     30  * string of characters that supports the replacement of a range of
     31  * itself with a new string of characters.  It is used by APIs that
     32  * change a piece of text while retaining metadata.  Metadata is data
     33  * other than the Unicode characters returned by char32At().  One
     34  * example of metadata is style attributes; another is an edit
     35  * history, marking each character with an author and revision number.
     36  *
     37  * <p>An implicit aspect of the <code>Replaceable</code> API is that
     38  * during a replace operation, new characters take on the metadata of
     39  * the old characters.  For example, if the string "the <b>bold</b>
     40  * font" has range (4, 8) replaced with "strong", then it becomes "the
     41  * <b>strong</b> font".
     42  *
     43  * <p><code>Replaceable</code> specifies ranges using a start
     44  * offset and a limit offset.  The range of characters thus specified
     45  * includes the characters at offset start..limit-1.  That is, the
     46  * start offset is inclusive, and the limit offset is exclusive.
     47  *
     48  * <p><code>Replaceable</code> also includes API to access characters
     49  * in the string: <code>length()</code>, <code>charAt()</code>,
     50  * <code>char32At()</code>, and <code>extractBetween()</code>.
     51  *
     52  * <p>For a subclass to support metadata, typical behavior of
     53  * <code>replace()</code> is the following:
     54  * <ul>
     55  *   <li>Set the metadata of the new text to the metadata of the first
     56  *   character replaced</li>
     57  *   <li>If no characters are replaced, use the metadata of the
     58  *   previous character</li>
     59  *   <li>If there is no previous character (i.e. start == 0), use the
     60  *   following character</li>
     61  *   <li>If there is no following character (i.e. the replaceable was
     62  *   empty), use default metadata.<br>
     63  *   <li>If the code point U+FFFF is seen, it should be interpreted as
     64  *   a special marker having no metadata<li>
     65  *   </li>
     66  * </ul>
     67  * If this is not the behavior, the subclass should document any differences.
     68  * @author Alan Liu
     69  * @stable ICU 2.0
     70  */
     71 class U_COMMON_API Replaceable : public UObject {
     72 
     73 public:
     74     /**
     75      * Destructor.
     76      * @stable ICU 2.0
     77      */
     78     virtual ~Replaceable();
     79 
     80     /**
     81      * Returns the number of 16-bit code units in the text.
     82      * @return number of 16-bit code units in text
     83      * @stable ICU 1.8
     84      */
     85     inline int32_t length() const;
     86 
     87     /**
     88      * Returns the 16-bit code unit at the given offset into the text.
     89      * @param offset an integer between 0 and <code>length()</code>-1
     90      * inclusive
     91      * @return 16-bit code unit of text at given offset
     92      * @stable ICU 1.8
     93      */
     94     inline UChar charAt(int32_t offset) const;
     95 
     96     /**
     97      * Returns the 32-bit code point at the given 16-bit offset into
     98      * the text.  This assumes the text is stored as 16-bit code units
     99      * with surrogate pairs intermixed.  If the offset of a leading or
    100      * trailing code unit of a surrogate pair is given, return the
    101      * code point of the surrogate pair.
    102      *
    103      * @param offset an integer between 0 and <code>length()</code>-1
    104      * inclusive
    105      * @return 32-bit code point of text at given offset
    106      * @stable ICU 1.8
    107      */
    108     inline UChar32 char32At(int32_t offset) const;
    109 
    110     /**
    111      * Copies characters in the range [<tt>start</tt>, <tt>limit</tt>)
    112      * into the UnicodeString <tt>target</tt>.
    113      * @param start offset of first character which will be copied
    114      * @param limit offset immediately following the last character to
    115      * be copied
    116      * @param target UnicodeString into which to copy characters.
    117      * @return A reference to <TT>target</TT>
    118      * @stable ICU 2.1
    119      */
    120     virtual void extractBetween(int32_t start,
    121                                 int32_t limit,
    122                                 UnicodeString& target) const = 0;
    123 
    124     /**
    125      * Replaces a substring of this object with the given text.  If the
    126      * characters being replaced have metadata, the new characters
    127      * that replace them should be given the same metadata.
    128      *
    129      * <p>Subclasses must ensure that if the text between start and
    130      * limit is equal to the replacement text, that replace has no
    131      * effect. That is, any metadata
    132      * should be unaffected. In addition, subclasses are encouraged to
    133      * check for initial and trailing identical characters, and make a
    134      * smaller replacement if possible. This will preserve as much
    135      * metadata as possible.
    136      * @param start the beginning index, inclusive; <code>0 <= start
    137      * <= limit</code>.
    138      * @param limit the ending index, exclusive; <code>start <= limit
    139      * <= length()</code>.
    140      * @param text the text to replace characters <code>start</code>
    141      * to <code>limit - 1</code>
    142      * @stable ICU 2.0
    143      */
    144     virtual void handleReplaceBetween(int32_t start,
    145                                       int32_t limit,
    146                                       const UnicodeString& text) = 0;
    147     // Note: All other methods in this class take the names of
    148     // existing UnicodeString methods.  This method is the exception.
    149     // It is named differently because all replace methods of
    150     // UnicodeString return a UnicodeString&.  The 'between' is
    151     // required in order to conform to the UnicodeString naming
    152     // convention; API taking start/length are named <operation>, and
    153     // those taking start/limit are named <operationBetween>.  The
    154     // 'handle' is added because 'replaceBetween' and
    155     // 'doReplaceBetween' are already taken.
    156 
    157     /**
    158      * Copies a substring of this object, retaining metadata.
    159      * This method is used to duplicate or reorder substrings.
    160      * The destination index must not overlap the source range.
    161      *
    162      * @param start the beginning index, inclusive; <code>0 <= start <=
    163      * limit</code>.
    164      * @param limit the ending index, exclusive; <code>start <= limit <=
    165      * length()</code>.
    166      * @param dest the destination index.  The characters from
    167      * <code>start..limit-1</code> will be copied to <code>dest</code>.
    168      * Implementations of this method may assume that <code>dest <= start ||
    169      * dest >= limit</code>.
    170      * @stable ICU 2.0
    171      */
    172     virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;
    173 
    174     /**
    175      * Returns true if this object contains metadata.  If a
    176      * Replaceable object has metadata, calls to the Replaceable API
    177      * must be made so as to preserve metadata.  If it does not, calls
    178      * to the Replaceable API may be optimized to improve performance.
    179      * The default implementation returns true.
    180      * @return true if this object contains metadata
    181      * @stable ICU 2.2
    182      */
    183     virtual UBool hasMetaData() const;
    184 
    185     /**
    186      * Clone this object, an instance of a subclass of Replaceable.
    187      * Clones can be used concurrently in multiple threads.
    188      * If a subclass does not implement clone(), or if an error occurs,
    189      * then NULL is returned.
    190      * The clone functions in all subclasses return a pointer to a Replaceable
    191      * because some compilers do not support covariant (same-as-this)
    192      * return types; cast to the appropriate subclass if necessary.
    193      * The caller must delete the clone.
    194      *
    195      * @return a clone of this object
    196      *
    197      * @see getDynamicClassID
    198      * @stable ICU 2.6
    199      */
    200     virtual Replaceable *clone() const;
    201 
    202 protected:
    203 
    204     /**
    205      * Default constructor.
    206      * @stable ICU 2.4
    207      */
    208     Replaceable();
    209 
    210     /*
    211      * Assignment operator not declared. The compiler will provide one
    212      * which does nothing since this class does not contain any data members.
    213      * API/code coverage may show the assignment operator as present and
    214      * untested - ignore.
    215      * Subclasses need this assignment operator if they use compiler-provided
    216      * assignment operators of their own. An alternative to not declaring one
    217      * here would be to declare and empty-implement a protected or public one.
    218     Replaceable &Replaceable::operator=(const Replaceable &);
    219      */
    220 
    221     /**
    222      * Virtual version of length().
    223      * @stable ICU 2.4
    224      */
    225     virtual int32_t getLength() const = 0;
    226 
    227     /**
    228      * Virtual version of charAt().
    229      * @stable ICU 2.4
    230      */
    231     virtual UChar getCharAt(int32_t offset) const = 0;
    232 
    233     /**
    234      * Virtual version of char32At().
    235      * @stable ICU 2.4
    236      */
    237     virtual UChar32 getChar32At(int32_t offset) const = 0;
    238 };
    239 
    240 inline int32_t
    241 Replaceable::length() const {
    242     return getLength();
    243 }
    244 
    245 inline UChar
    246 Replaceable::charAt(int32_t offset) const {
    247     return getCharAt(offset);
    248 }
    249 
    250 inline UChar32
    251 Replaceable::char32At(int32_t offset) const {
    252     return getChar32At(offset);
    253 }
    254 
    255 // There is no rep.cpp, see unistr.cpp for Replaceable function implementations.
    256 
    257 U_NAMESPACE_END
    258 
    259 #endif
    260